Battery separator



FI G.

INVENTOR.

FIG 2 March 23, 1954 J. B. BRENNAN BATTERY SEPARATOR Original Filed Jan.8. 1949 FIG. 4

FIG.7

Patented Mar. 23, 1954 UNITED STATES PATENT OFFICE 69,863. Divided andthi 1949, Serial N0. 90,609

This invention relates to storage battery electrodes and electrolyticcell electrodes and especially to porous dielectric separators orspacers for such electrodes.

This invention is a division of my (zo-pending application Serial No.69,863, led January 8, 1949, insofar as it contains common subjectmatter.

According to this invention I directly apply the porous dielectricspacer described in the above application to either one or more or allsides of an electrode after its having been impregnated with activematerial or pasted or coated therewith.

When the porous electrode containing active material therein and thereonas for a storage battery is coated with dielectric particles as by spraydepositing one or more layers thereover while being held at atemperature to cause a porous deposit of molten particulate material asof polythene or polystyrene thereover a porous pocket or envelope isproduced thereby which contains the electrode and active materialtherein for each or alternate plates of the storage battery assembly sothat shedding of the active material is eliminated while permitting freepassing of ions and free gassing of the electrolytic cell and electrodestherein.

The porous pocket or envelope for each electrode can be made by spraydepositing the strip electrode material with particulate molten or tackyparticles of dielectric material so that a porous envelope is producedabout the porous electrode and the active material with which the porousmetal part of the electrode has been coated and/or impregnated or lledand coated by eleotroformation of the active material therein or thereonor by a combination of these processes.

In any case according to this invention a porous electrode in its porousenvelope of dielectric material containing active material in contactwith its porous metal portion is produced.

Electroformation, or impregnation of the porous electrode can beeffected after the exterior porous dielectric coating of this inventionis applied so that in this case the active material is formed andadherently deposited on and in the interstices of the porous metalportion of the electrode within its porous envelope.

Also the porous dielectric coating can be spray `deposited afterelectroformation, impregnation or` pastingof the porous metal electrode.

Another way in which the porous particulate layer may be applied to theelectrode according s application April 30,

4 Claims. (Cl. 13G-147) to this invention is to sift or spray theparticles through a fog or spray of solvent therefor so as to wet samewith said solvent spray thereby rendering the exterior of said particlestacky and simultaneously depositing the so-wetted dielectric particlesin a layer over the outside of the porous metallic electrode andthereafter bake the so-coated electrode under the flow temperature ofthe dielectric particles.

Another way in which the objects of this invention may be carried out isto place the porous electrode in a smooth polished pocket and then ll upsaid pocket with loose particles of dielectric material and then sprayor dip the layer in a solvent as toluol and remove quickly and dry andbake whereby the particles will stick to each other to form an adherenttough coating and yet remain porous.

Another Way in which the particulate coating may be made according tothis invention is to coat one side of an electrode with a layer of dryparticles with a doctor blade'tc level olf the layer to a uniform heighthaving the particles extend over and outside the edges of said electrodethen spray same with a fog spray gun with a solvent such as toluol thenbake same and turn over and coat the opposite side of the said electrodein a similar manner and then bake whereupon the entire electrode excepta portion of its terminal will be enclosed in and surrounded by anadherent porous particulate layer whereby the thickness thereof will beuniform.

Another way is to deposit particles all over the exterior of theelectrodes with solvent wetted dielectric particulate plastic so thatthe edges and faces are uniformly coated and then bake same at atemperature just sufficient to harden the particles but under the owtemperature thereof.

Strips of aggregated plastic particles may be built up in layer form andwetted with a solvent to render the exterior of the particles plasticand pieces of `such strips may be formed by light pressure in a mold andbaked to produce a cuplike or hollow shape two of which may be appliedto each side of an electrode to enclose same.

The strips so produced may be shaped by other means to conform to theexterior of the electrodes and to form an enclosure therefor.

In case a series of electrodes are to be assembled in facialjuxtaposition as is usual in an electrolytic cell only one side and theedges of each ,electrode need be coated and the coated 'sides maybe'joined as by cement at their edges and the single'side coatedelectrodes stacked so that a unitary enclosure for the stack results.

It is also preferable in some cases to coat the assembled stack withadditional porous particulate aggregates or layers so that the stack ofplates and separators can be made to t exactly or in spaced relationinto the container for the stack so that the porous exterior enclosurefor the electrodes serves also to position the assembly in the containerand retain it 'in position as well as to retain the electrolytetherearound and to permit free circulation therearound and therein.

In other words the voids in the container having the stack therein maybe filled with dielectric particles and then baked to fuse the particlesinto a porous unit.

When the material of the porous electrode enclosure is suitable as forinstance polystyrene particles these can be wetted on the outside withsolvent and if the container is of like material they can be fittedtogether so that the Vporous `plate enclosure is cemented to theimpervious container and subsequent movement in use is prevented.

The electrodes for Vuse with my present invention are preferably ofporous metal particles in thin exible strip form of .010 to .050 thick.Porous spray deposited zinc can be used effectively as a negativeelectrode in a sodium zincate or potassium zincate electrolyte with apositive porous spray deposited nickel plate for a storage battery.

Porous nickel may be used for each electrode if coated or impregnatedwith suitable active material.

I have found that a spray deposited electrode of nickel having a moltenspray deposited coating of porous cadmium thereover `and then pastedwith cadmium oxide or electroformed therewith works satisfactorily as anegative electrode with a spray deposited porous nickel electrodeimpregnated with or pasted with'nickelous hydroxide works satisfactorilyas a positive electrode for a storage battery.

The impregnation may be accomplished by vacuum and pressure alternatelywhile electroforming simultaneously while the electrodes individually orafterV being united in stacks with J separators are immersed in suitableforming electrolyte.

A unitary electrode and separator assembly is produced according to myinvention which will withstand rugged physical conditions.

I have found that it is preferable to use pure self-supporting porousparticulate metal strip and that supporting grids are unnecessary tomake suitable electrodes when spray depositing in continuous strip formis utilized to make these electrodes.

It is desirable to keep the porous electrodes and the active materialassociated therewith of uniform thickness and area as well as theseparators enclosing same so that if pressuresare applied to theassembly in placing same in a container or thereafter will be uniformlydistributed and thereby the active materials will be in uniformconductive relationship with the porous metal electrode which isessential to uniform and good performance. y

In a lead acid type battery the porous particulate lead electrodescontaining active material in their interstices may be made rugged andvery strong by coating with porous dielectric spray depositedenclosures.

The active lead oxides may be made into briquettes or plates and thenspray `coated with porous lead and then this structure spray coated withporous dielectric plastic particles to make aV unitary sell-supportingelectrode.

In applying the dielectric particles to the electrodes according to myinvention when for example polystyrene particles are used these may bein the partially polymerized condition such as are generally used forextrusion or molding purposes and after they are applied to theelectrode or after they are stuck together with a plasticized exteriorin ystrip or hollow form they are further reacted and made more strongand stable by baking at from 250 F. to 550 F. either in an open heatchamber or in a pressurized heat chamber while maintaining the base at350 F. or less for just enough time and temperature to bond strongly butnot to melt completely.

One further example regarding the use of polythene in practicing theinvention is to provide such material in nely divided particles. Suchparticles of material are placed in a container and agitated, as with anair b1astplus a stirring device if desired, and are picked up by anairrsyphon. These picked-up particles are sprayed through a flame madeup of a mixture of a combustile gas like propane or ordinary coal gashaving oxygen mixed therewith, or with air alone, to obtain atemperature of from about 500 F. to 1500 F. and to provide an air blastfor conveying the powdered material to the flame. The actual spray gunwould be held about l0 to 20 inches from the base on which it is desiredto deposit the material and the base normally is a shiny surface towhich the sprayed material will not adhere readily and it is preferablycooled as by some fluid coolant such as air or Water and the materialstripped from such base after a layer of deposited material is formed.The powdered material is thus sprayed through the flame and the sprayiield on repeated passes of the spray gun over the base is overlapped tosecure a uniform deposit on the base, which preferably is constantlymoving. A very highly polished aluminum oxide surface may be provided onthis base. The base extracts heat from the particles when they collidewith or deposit on the base and so aids in solidifying the particlesbefore they completely coalesce.

Also if preferred the dielectric plastic particles may be made 4morespherical in shape if they `are dropped through a heated zone for aconsiderable distance in spray depositing when molten. This givesgreater porosity because of the exterior great surface of the spheres. Y

I have also found that spherical metal particles are more preferable inmaking battery electrodes and their spheroidal shape is best retained bydropping them through a considerable distance under heat suicient tofuse the outside of the particles at lo-w velocity so that upon andafter deposition on a chilled base surface they retain their spheroidalshape and are welded together at adjacent points on their surfaces.

This procedure also gives greater porosity to the dielectric particlelayer or body or coating.

It is also contemplated according to this invention to use laminatedlayers of porous-dielectric material over and around-the electrodes andof dierentsize particles ii. desired. p

When making laminated lcoatings for electrodes it is preferable to usefor example glass fabric adjacent the metal electrode or asbestos paperin thin layer form and thereover apply the particulate dielectricenclosure. Also a layer. of ne dielectric particulatematerial 4may befirst :applied to the metal'ele'ctrode and a coarser layer thereover toadvantage.

Serrations and hollow grooves may be incorporated into the exterior ofthe porous dielectric coating to facilitate gassing between eachelectrode if desired.

Referring to the drawings which accompany and are a part of thespecications of this patent application:

I, Fig. 1, is a section of a metal electrode having active materialassociated in conductive relationship with the metal thereorn and havinga terminal tab 2, Fig. 1, extending therefrom. 3. Fig. 1, is a sectionalView of the porous particulate dielectric coating of the electrode l,Fig. 1, partially extending about the terminal 2, Fig. 1.

Fig. 2 is a section of the electrode shown in Fig. 1 taken on the lineA-A Fig. 1 wherein like numerals indicate like parts.

Thus I, Fig. 2, illustrates a section of a porous electrode as of lead,zinc, nickel, iro-n or other battery metals spray deposited or sinteredpreferably and having active material associated therewith and 2, Fig.2, is the terminal section thereof and 3, Fig. 2 is a section of theporous particulate dielectric support and spacer thereover.

In Fig. 3 an assembly of electrodes coated with porous dielectricparticulate coatings is shown in face-to-face relation or slightlyspaced if preferred over at least a part of the area of the exteriorparticulate coating of `each electrode.

The electrodes shown in Fig. 3 are each coated with porous dielectriclayer over all their active bodies and are preferably cemented or curedtogether so as to become a unitary structure.

In Fig. 3 the porous dielectric coatings 3, Fig. 3, are shown adjacenteach other but it may some times be preferable to insert additionalspacers (not shown) between each electrode coated with porous dielectricpreferably of like material to the porous dielectric electrodeenclosures 3, Fig. 3, to give additional electrode spacing.

Such additional spacers may be cemented to the spacers 3, Fig. 3, andbetween same and may be vertical rods or tubes closely aligned or sheetsof porous dielectric material or brous material.

Fig. 4 of the drawings illustrates a section through a modification ofthe electrode of the invention and wherein a porous metal sheet laencloses a briquet 4 made from active lead oxide. A terminal 2a is insuitable contact with the metal sheet la and the briquet 4 and theentire active portion of the electrode is enclosed by a dielectricparticulate layer 3a.

Fig. 5 is a section of a further electrode of the invention wherein aporous particulate metal layer Ib is vshown and it has active materialassociated therewith whereas a terminal 2b is also suitably securedthereto. This metal layer I b is enclosed or surrounded by a layer of,for example, glass fabric 5 that is positioned immediately adj acent theporous metal electrode while a layer 3b of particulate dielectricmaterial is positioned over this glass fabric 5.

Fig. 6 shows a porous metal electrode Ic which has a terminal 2c securedthereto and a layer of fine dielectric particles is positionedthereover, which layer is indicated by the numeral 3c. A layer 6 ofcoarser dielectric particles is superimposed on the layer 3c.

Fig. 7 shows another electrode assembly of the invention in section andporous electrodes, having active material in the interstices thereof,are indicated by the numeral I d. Suitable electrode terminals 2d areattached to the porous electrodes and a layer 3d of dielectricparticulate material is positioned over at least one race of each of theelectrodes. Additional porous spacers i are interposed -between theoutside of the layers 3d of the adjacent surfaces of the differentelectrodes. The porous spacer layers l' may consist of rods, orparticulate layers and preferably are porous.

Other thermosetting or thermoplastic coating materials may be used toachieve the purposes of my invention such as for example B-stage phenolformaldehyde resin spray deposited in molten parti-cles and then heatedto cure in a gas or liquid pressure vessel.

The particles must be so close to each other in layer form or in a moldthat they will unite on exterior heating only and quickly prior tobecoming entirely molten in order to retain the interstices between theparticles in the layer of shape.

Having described my invention what I claim is:

1. In combination, an electrolytic cell electrode carrying activematerial, and a dielectric support and spacer layer of plastic materialintegrally bonded to and extending in substantially continuous relationover a portion of said electrode suilcient to substantially support andenvelop the same, said layer comprising spray deposited particles or"said plastic material welded together at adjacent points on the surfaceof the particles with interstices between the particles rendering thelayer porous and electrolyticaily permeable.

2. The combination of an electrolytic cell electrode and an integrallybonded dielectric .support and spacer layer as defined in claim 1 inwhich said layer is iornied by spray deposited particles of materialfrom the group consisting of polythene, polystyrene and phenolformaldehyde resins.

3. In combination, an electrolytic cell electrode, and a dielectricsupport and spacer layer of plastic material integraily bonded to andextending in substantially continuous relation over a portion of saidelectrode sufficient to substantially support and envelop the same, saidlayer comprising spray deposited particles of said plastic materialwelded together at adjacent points on the surface of the particles withinterstices between the particles rendering the layer porous andelectrolytically permeable.

4. The combination of an electrolytic cell electrode and an integrallybonded dielectric support and spacer layer as defined in claim 3 inwhich said layer is formed by spray deposited particles of a syntheticresin material Which is non-reactive with the electrolyte.

JOSEPH B. BRENNAN.

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